Direct halogenation of the C1 H bond in pyrrolo[1,2–a]quinoxalines

Although pyrrolo[1,2–a]quinoxalines are important in pharmaceutical research and organic synthesis, diversification of these compounds is still limited. Herein we have developed a method for the selective chlorination of the C1H bond in 4-aryl pyrrolo[1,2–a]quinoxalines. The reactions proceeded in the presence of NCS as a chlorinating agent, a catalytic amount of DMSO, and CHCl3 as the solvent. Various functional groups including fluoro, chloro, and methylthio were compatible with the reaction conditions. Heterocycles located at the C4 positions of pyrrolo[1,2–a]quinoxalines such as furan, thiophene, or pyridine were also compatible with the reaction conditions. The bromination of pyrrolo[1,2–a]quinoxalines was successful in the presence of CuBr2 as a brominating agent, K2S2O8 as an oxidant, and toluene as the solvent.